G protein-coupled receptor 119 (GPR119) is a new diabetes drug target. GPR119 agonists have been the focus of new drug development efforts of many multinational pharmaceutical companies. Among a series of small-molecule GPR119 agonists developed by GlaxoSmithKline, GSK252A of the following formula has the most outstanding performance:

The GSK252A molecule includes a novel pyrrolopyrimidine bicyclic structure. One important method of constructing such a bicyclic structure is a ring-closing reaction using (4,6-dichloro-pyrimidin-5-yl)-acetaldehyde. Therefore, the synthesis of (4,6-dichloro-pyrimidin-5-yl)-acetaldehyde is of remarkable importance to the subsequent development of GSK252A and other similar active substances based on the pyrrolopyrimidine bicyclic structure.
Current synthesis of (4,6-dichloro-pyrimidin-5-yl)-acetaldehyde, the compound of the following formula I, relies mainly on an oxidation reaction for creating an oxoethyl group in position 5. One example of this approach is disclosed in WO2010/9195, in which the synthesis is based on the compound of the following formula II and uses potassium osmate as an oxidant, according to the following equation:

WO2003/105770 discloses the synthesis from the compound of the following formula III, in which osmium tetroxide is used as an oxidant, according to the following equation:

However, oxidation reactions are generally associated with a high risk and low controllability and thus have unsatisfactory final yields. In addition, osmium tetroxide and potassium osmate are not suitable for use in the production of pharmaceutical intermediates and industrialized production because they are less water soluble, creates difficulties in post-processing, and tends to remain in the final products.